1. Field of the Invention
The present invention relates generally to a multihop relay wireless communication system. More particularly, the present invention relates to an apparatus and method for reducing interference of a neighbor cell in the multihop relay wireless communication system.
2. Description of the Related Art
When adopting a Time Division Duplex (TDD) scheme, a wireless communication system communicates data by dividing a frame consisting of one frequency band into a transmit interval and a reception interval using time resources. The wireless communication system can adjust an amount of resources allocated to UpLink (UL)/DownLink (DL) according to a traffic volume. That is, the wireless communication system can adjust a size of the transmission interval and the reception interval based on the traffic volume.
Accordingly, when a TDD based wireless communication system consists of multiple cells, each cell of the wireless communication system can allocate different resources to the UL/DL according to the traffic volume. In this case, the wireless communication system may suffer interference of a neighbor cell because the UL/DL timing of the neighbor cells does not match as shown in FIG. 1.
FIG. 1 illustrates a construction of a conventional TDD system.
In FIG. 1, a first Base Station (BS) 101 communicates with a first Mobile Station (MS) 103, and a second BS 111 communicates with a second MS 113. The first BS 101 and the second BS 111 communicate with the MSs 103 and 113, respectively, using the TDD scheme. Thus, the first BS 101 and the second BS 111 can allocate different amounts of resource to the UL/DL according to the traffic volume with the MSs 103 and 113.
When the BSs 101 and 111 allocate different amounts of resource to the UL/DL, an interference of a neighbor cell can be caused because UL/DL timings for the BSs 101 and 111 do not match. For instance, when the first BS 101 sends a DL signal to the first MS 103 and the second MS 113 sends a UL signal to the second BS 111, the UL signal of the second MS 113 acts as considerable interference to the DL signal received at the first MS 103. As a result, the first MS 103 is subject to reception performance deterioration due to the interference of the second MS 113.
As discussed above, when the amounts of the UL/DL resource are different in the neighbor cells in the TDD wireless communication system, the MS in the cell boundary is subject to the deterioration of the reception performance because of the interference of the neighbor cell.
A recent wireless communication system provides a relay service using a Relay Station (RS) to expand a service coverage area without a shadow area or to increase a transmission speed of an MS in the cell boundary.
When the wireless communication system provides the relay service, and the timings of the UL/DL of a BS do not match with a neighbor BS, an RS or an MS in the cell boundary may suffer the deterioration of the reception performance because of the interference of the neighbor cell.